The present invention relates to a liquid crystal display device and a pixel inspection method therefor. For example, the present invention relates to a liquid crystal display device suitable for accurately inspecting pixels, and a pixel inspection method therefor.
A subframe driving method is known as one of halftone display methods employed in liquid crystal display devices. In a subframe driving method which is one type of time base modulation method, a predetermined period (one frame that is a unit for display of one image in the case of moving pictures, for example) is divided into a plurality of subframes, and pixels are driven in a combination of subframes according to a gradation for display. The gradation for display is determined according to the ratio of a pixel drive period occupied in a predetermined period, and this ratio is specified by the combination of subframes.
In the liquid crystal display devices which employ this subframe driving method, one is known in which pixels are individually composed of a master latch, a slave latch, a liquid crystal display element, and a plurality of switching transistors.
In this pixel, one bit of first data is applied to an input terminal of the master latch through a first switching transistor, and when a row select signal applied through a row scanning line is active, the first switching transistor is turned on and the first data is written into the master latch.
After the writing of data into the master latches provided in all the pixels is completed, second switching transistors provided in all the pixels are turned on in a subframe period. As a result, the data that are written into the master latches provided in all the pixels are simultaneously read out to the slave latches, and the data that are written into the slave latches are applied to the pixel electrode of the liquid crystal display element. In each subframe period, similar processes are performed on all the pixels. As a result, a desired gradation display can be performed with combinations of a plurality of subframes constituting one frame.
The periods of the plurality of subframes constituting one frame are allocated to the same or different predetermined periods. For example, in each pixel, when a maximum gradation display is performed (white is displayed), the display is performed on all the plurality of subframes constituting one frame. When a minimum gradation display is performed (black is displayed), the display is not performed on all the subframes constituting one frame, and subframes for display are selected according to the gradation for display in a case where the other gradation displays are performed. This liquid crystal display device of the related art uses digital data indicating a gradation as input data and adopts a digital driving method using a two-stage latch configuration.
A method for inspecting pixels by connecting adjacent pixels is known as a pixel inspection method. For example, Japanese Patent No. 5765205 discloses a pixel inspection method for a liquid crystal display device including pixels each including a master latch unit composed of an SRAM and a slave latch unit composed of a DRAM. In the pixel inspection method, switching means capable of rendering right and left adjacent pixel electrodes conductive is provided and a pixel inspection is performed by reading out data input to a first pixel from a second pixel.